This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present invention. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present invention. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
Seismic surfaces are horizons that have been tracked through 2D or 3D seismic data, which represent and generally follow subterranean reflector surfaces. They generally correspond to boundaries between layers of rock, with everything below the horizon older than everything above the surfaces, hence represent boundaries of equivalent time.
Since the 1970's, geoscientists have used the concepts of seismic stratigraphy to interpret and label the key types of seismic stratigraphic surfaces—sequence boundaries (SBs) and flooding surfaces (FSs). One fundamental concept of seismic stratigraphy is that sequence boundaries (SBs) and flooding surfaces (FSs) divide seismic data into chronological packages, forming boundaries of genetically related packages of strata called seismic sequences and seismic systems tracts. FIG. 1 is a schematic depositional sequence model illustrating unconformity 101, transgressive surfaces 102, depositional geometries, and key depositional packages including lowstand fan (potential reservoir) 103, lowstand wedge (potential seal) 104, and distal highstand (potential seal) 105. These surfaces types can be characterized and identified based on the geometry of surrounding seismic reflection terminations (onlap 201, downlap 202, toplap 203 and erosion or truncation 204) (FIG. 2), their own characteristics (e.g., amplitude, dip, smoothness or rugosity, continuity, etc.), and/or the characteristics of their bounding seismic facies (e.g., amplitude, frequency, continuity, geometry, seismic geomorphology, etc.). Application of these concepts has proven to be a robust technique to help predict qualitative and quantitative subsurface properties, including stratigraphic relationships, ages, environments of deposition, depositional facies, systems tracts, lithologies, porosities, and other rock properties, many of which are important in hydrocarbon exploration or development (Vail et al., 1977; Mitchum et al., 1977; Van Wagoner et al., 1988; Brown and Fischer, 1977; Neal and Abreu, 2009) (see FIG. 1).
Traditionally surfaces in seismic data have been tracked interactively along a 2D line or volume of seismic data. Computer-based surface picks were initially interpreted using drawing or tracking software. Subsequent innovations allow surfaces to be tracked automatically or semi-automatically through 2D or 3D seismic data nearly instantaneously using software now routinely available in numerous commercially available software products for geophysical interpretation (e.g., Viswanathan 1996 U.S. Pat. No. 5,570,106); Pedersen, 2002, GB Patent No. 2,375,448; Admasu and Toennies, 2004; James, WO 2007046107). With these methods, interpreted surfaces are based on one or more seed point(s) or seed track(s) provided by the interpreter, with the final interpretation interactively accepted or revised by the interpreter. Options or ambiguities in interpretation, such as which branch to take when a surface splits, are frequently resolved by application of seismic stratigraphic concepts by the seismic interpreter. One component of seismic interpretation, then, is the gradual development of a conceptual geologic or seismic stratigraphic framework model of the region represented by the seismic data. Part of this is implicit or explicit classification or labeling of surfaces as FSs, SBs, or other meaningful geologic or geophysical surface types by the interpreter as a guide to executing the interpretation and subsequent procedures. The interpreter does this based on the seismic reflection geometries and terminations (onlap, downlap, truncation and toplap), seismic characteristics of the surface itself (amplitude, dip, smoothness or rugosity, continuity, etc.), and seismic facies characteristics of the bounding intervals, following the concepts of seismic stratigraphy. Judgment and evaluation based on the developing conceptual geologic model is done at several points in the interpretation process, including selection of which surfaces to track, what choices to make when encountering ambiguities, deciding whether to accept or revise a surface, and selecting areas of interest for subsequent analyses, interpretation, or visualization, for example, as potential hydrocarbon reservoirs, source facies, or seal facies.
Further innovations in the interpretation of seismic surfaces now provide methods of automatic picking a dense set of surfaces, also known as “stacks of surfaces” or “global interpretation” in seismic volumes. These methods refer to interpretation of many or all surfaces, or portions of surfaces in seismic volumes. Geologically-motivated mathematical rules or user-guidance may be employed at decision points to resolve ambiguities, such as a faults or where reflectors merge or branch, and/or overlapping or crossing of surfaces. In some cases, sets of surface parts may be the final product. These extend over only portions of seismic volumes, often terminating where further correlation is ambiguous (i.e., “horizon patches” of Imhof et al., 2009). These sets of surfaces or surface parts can be produced relatively rapidly from 2D lines or 3D volumes of seismic data with little to no user interaction.
Examples of methods for automatically generating “stacks of surfaces” or “stacks of surface patches” that generally follow seismic events such as peaks, troughs, or zero crossings include:                Li, Vasudevan and Cook (1997) describe a method called seismic skeletonization to automatically pick seismic events and assign attributes to each event. Events are correlated across neighboring traces so that changes in dip are minimized.        U.S. Pat. No. 7,248,539 to Borgos (“Extrema Classification”) (2007) discloses a method of automated interpretation of seismic reflectors and fault displacement calculations, based on classification of seismic waveforms along reflectors, specifically around extrema positions, where they gain improved performance in structurally complex regions.        Stark (U.S. Pat. No. 6,850,845B2)) describes a method for producing detailed seismic interpretation (and geologic time volumes or relative geologic time volumes) by applying phase unwrapping to instantaneous phase transform of a seismic volume.        Imhof et al., (2009) describe a method also called skeletonization for transforming a seismic volume to a large number of reflection-based surfaces that are topologically consistent, that is, having no self-overlaps, local consistency, and global consistency. A set of surfaces are created and labeled monotonically in a top-down fashion.        Pauget et al (WO 2010/067020 A2) describe a method to create a relative geologic age model by trace correlation which generates a global interpretation of seismic volumes. Software to apply their technology called Paleoscan is commercially available through a French company called Eliis.        deGroot and Qayyum (2012) describe a method to generate a dense set of surfaces throughout a 3D seismic volume based on applying a 3D auto tracking algorithm to a dip/azimuth field. This method is marketed as the “HorizonCube” of dGB Earth Sciences.        
As described above, interactive seismic interpretation is nearly always done using a conceptual geologic model. The model is used to help select which surfaces to track, what choices to make when encountering ambiguities, whether to accept or revise a surface, and selection of areas of interest for subsequent analyses. When automatically generating stacks of surfaces or surface patches, such as occurs when applying the methods cited above, this step has not yet occurred. The output is a set of unclassified surfaces.
Surface Labeling
Other methods of surface clustering or labeling have been developed. These include: U.S. Pat. No. 6,771,800 (“Method of Chrono-Stratigraphic Interpretation of a Seismic Cross Section or Block”) to Keskes et al. (2004) discloses a method to transform seismic data into the depositional or chronostratigraphic domain. They construct virtual reflectors, discretize the seismic section or volume, count the number of virtual reflectors in each pixel or voxel, and renormalize this histogram. By doing this procedure for every trace, they create a section or volume where each horizontal slice approximates a surface indicating a geologic layer deposited at one time. This can be used by an interpreter to determine sedimentation rates, highlighting geologic hiatuses, which are surfaces of non-deposition.
Monsen et al. (“Geologic-process-controlled interpretation based on 3D Wheeler diagram generation,” SEG 2007) extended U.S. Pat. No. 7,248,539 to Borgos. They extract stratigraphic events from the seismic data and categorize them into over/under relationships based on local signal characteristics, deriving a relative order of patches using a topological sort. Flattened surfaces are then positioned in this relative order to allow a user to interpret the surface type by relative age, position, and basinward and landward extents, or through transformation to the depositional Wheeler domain (Wheeler, 1958). Wheeler methods can work in shelf margin depositional environments to determine surface types, but may not work in other settings, such as continental or deepwater. They also do not compute confidence measures.